Rotary hair clipper



June 8, 1943. R. PENNEY ROTARY HAIR CLIPPER INVENTOR .Pen may Filed May 22, 1939 2 Sheets-Sheet [fol/27% L %TTORNEY June 8, 1943. R. 1.. PENNEY ROTARY HAIR CLIPPER 2 Sheets-Sheet 2 Filed May 22, 1939 INVENTOR .zqe/uzgy TORZ -EY Patented June 8, 1943 UNITED STATES PATENT OFFICE ROTARY HAIR CLIPPER Robert L. Penney, Brooklyn, N. Y.

Application May 22, 1939, Serial No. 274,916

7 Claims.

This invention relates generally to improvements in hair clippers and particularly to such power driven devices as are adapted to be used for shaving human hair.

In my prior application filed January 7, 1939, Serial Number 249,747, I have disclosed an apparatus of the type above described in which a rotating cylindrical cutter cooperates with a shearplate to shear and shave hair. The present construction embodies the same general arrangement of parts as the apparatus described in the prior application and the principal object of this invention is to improve the cutter shown in said prior application so as to make the cutter stronger and longer wearing yet so simplifying this modified design that the present cutter is less expensive to manufacture than the wire-wound cutter previously disclosed.

In the accompanying drawings,

Fig. 1 is a side elevation of my improved hair clipper.

Fig. 2 is a greatly enlarged View of the upper part of Fig. 1, partly in cross section.

Fig. 3 is a cross section of Fig. 2 taken on the plane of the line 3-3 of Fig. 2.

Fig. 4 is a perspective view of Fig. 2 with the shearplate and cutter removed.

Fig. 5 is a perspective view of the bottom of the shearplate.

Fig. 6 is a plan view of a metal sheet from which the cutter member is stamped showing its appearance after the first manufacturing operation has been completed.

Fig. 7 is a cross sectional view of Fig. 6 taken on the plane of the line l'l.

Fig. 8 is an end view of the cutter of Fig. 6 after the forming operation.

Fig. 9 is a sectional view of a modified form of shearplate.

Fig, 10 is a schematic diagram illustrating the various positions of the bars of the cutter relative to the bars of the shearplate during one revolution of the cutter member.

Referring to the drawings, a preferred'construction comprises a housing H), the bottom tubular section of which encloses a small electric motor it having a motor shaft 12 which is supported in suitable bearings l3 contained in the housing It. The shaft I2 includes an extension M, the upper end of which is provided with a cross pin l5 which cooperates with diametrically opposite slots l8 and I! in the lower end of the cutter member 3. This cutter I8 is thereby loosely coupled and removably fastened to the shaft [4 and turns with it.

The cutter i8 is contained in a tubular housing or shear member 19 which is' detachably connected to the reduced head portion 20 of the main housing It. This head 20 is formed with a dovetail slot 2|. An integral dovetail extension 22 on the bottom of the shear member l9 fits, in the dovetail slot 2! and is guided into position by the walls of said slot. The bottom edge 23 of the extension 22 is slightly tapered to facilitate entrance into the slot. On its bottom surface, this extension 22 is formed with a tapered, halfround, central groove 24 to about midway its length where it terminates in ahalf-round cross channel 25. I

A spring pressed ball 26, having a slightly larger radius than the channel 25, is embedded in the head 20 in such manner that a portion thereof projects into the slot 2|. This ball detachably holds the shear member I9 in fixed position in the head 20, and the channel 25 is in such position relative to the spring-ball 25 as to tend to keep the shearplate I9 pressed toward the motor housing I0 when these parts l9 and I0 are assembled.

The shear member I9 is offset bored to leave a thin front wall which includes helical bars 28, cut in screw-thread form, to produce cutting elements of the same pitch and lead as the bars of the cutter. That is, these teeth are screw-thread in formation, both in elevation and cross section, as each tooth 28 has a constant and uniform axial lead similar to the thread of a helicoid. The bars 28 are so cut or swaged as to be either triangles or isosceles trapezoids in cross section so that, when cooperating with the similarly shaped bars 29 of the cutter, the coacting edges of both shear member and cutter bars have back bevels or rakes which tend to facilitate the cutting action. However one or both of these sets of bars 28 and 29 could alternately be made half-round or semicircular in cross section, as shown in Fig. 10.

In the construction shown in myprior application, the cutter member is in the form of a helical compression spring, each turn of which is used in practice as a cutting bar cooperating with identically spaced bars on the shear member, While this previous construction shows cutter bars which are continuously connected, such a continuous design is not essential for the proper operation of the device. That this is true will be made obvious by reference to Fig. 10 in the accompanying drawings where 30 and 3| indicate adjacent shear members'and 32 indi- ,.cates one turn of the continuous cutting element of the helical cutter member, all being shown in schematic cross section. As an example, if this shear member is cut and this jcutter is wound to 28 pitch, then the lead will be .0357" or roughly .036, so that the distance from the right edge of member 30 to the right edge of member 3! will be .036". If, moreover, the cutting elements of both shear member and cutter are made of the same width, and assuming this width to be .024, then the spaces 33 between the various elements will be .012"; Since the lead isms",

each revolution of the cutter will advance a cutter element .036 and each one-third revolution will advance this element .012".

In the first step a of Fig. 10, the cutting turn 32 is matched and aligned with the member 30 so that the space 33 between the bars of the shear member is free and open for the admittance of hair to be out. In the second step b, the turn 32 has rotated one-third of a revolution and therefore has advanced .012", shearing the hair in the space 33, by and between the turn 32 and member 3!, and then closing off the space 33. In the third step c the turn 32 has turned another one-third part of a revolution and has advanced another .012 but still covers the space 33. In the last step (2, turn 32 has completed its revolution and has advanced the third .012 and is now aligned with the member 3| while the space 33 is now uncovered and again free and open to admit hair to the cutter. Thus it will be seen that, for one-third of each revolution, as shown in the third step c of Fig. 10; the space 33 is closed ofi by the turn 32, whether that turn be continuous or not. In other words, if all the turns 32,34, etc., were to be connected together for one-third of their effective perimeters, there would be no change in the amount of time that the space 33 is open to receive hair in each revolution of the cutter and, as regards shearing, the

operation would be the same as for the airspaced type of cutter shown in my prior application. This being so, applicant proposes in effect to connect all the turns of the helically wound cutter, for a minor portion of its circumference, eliminating the necessity of manufacturing this part of specially drawn wire and entirely dispensing with the use of a connecting cutter plate as shown in my previous disclosure. Instead applicant now proposes to make this cutter member of one piece of thin steel sheet.

As shown in Figs. 6, 7 and 8, a steel sheet 35, $5" or less in thickness, is stamped or swaged with a plurality of parallel V-shaped channels or grooves 36 part way down into the sheet. These V-grooves 36 are of a length corresponding to or more of the width of the sheet 35, are

set over to an angle relative to the edges of the sheet 35 corresponding to the helix angle of the finished part, and are of thesame number-perinch as the bars of the cooperating shear member.

Only a single series of these grooves is provided leaving a solid wall on all sides thereof. The sheet 35 is now rolled across its width, with the grooves 36 inside, and is formed into a cylindrical tube having a small space 3'! where the parallel edges of the sheet 35 tend to meet and join. This roll forming is done on a threaded mandrel or work arbor having the same pitch as the pitch of the grooves 36 so that the grooves 36 are givena screw-thread form while being rolled. The outside diameter of this formed tube is now ground down to semi-finish size, removing the excess metal shown by the dotted line 33 in Fig. 8 and disclosing the slots 39 produced by removing the apices of the V-grooves 33, thereby forming the bars 29.

If the sheet used to manufacture this cutter tube is of a certain type of material, such as 18-8 chromium-nickel steel, it will be found that the swaging plus the roll forming in the process of manufacture has work-hardened the sheet to a considerable degree so that the finished tube has, in effect, a spring temper and the edges which form the space 31, when pressed together, ,will react and spring back to their open positions when the pressure is removed. Alternately, a high carbon tool or spring steel may be used and quenched and spring tempered after forming and before grinding.

If the outside diameter of the cutter tube I8 is now finished with a lap which has a bore slightly smaller than the ground diameter of the tube, the piece will be finished round while under its own spring pressure and will have that outward spring pressure when journalled in a shear member having a bore of the same size as the finishing lap. This spring pressure in the cutter will keep the cutter and its cooperating shear member in proper shearing contact, compensating for any wear of either the-cutter or the shear member or both.

It will thus be seen that this improved cutter is interchangeable with, and that it substitutes for, the helically wound cutter shown in my prior application and that this improved design is identical in shearing operation to the helical cutter. That is, the same ratio of hair-entering and shearing time-periods can be produced in either type of cutter and both types are self-springpressed, requiring no external springs to insure shearing contact. The helical cutter was threadedly engaged and otherwise permanently fastened to a cutter plate by the whole perimeter of that part but in the present construction it is obvious that, if such a cutter plate were to be securely fastened by its entire circumference to the cutter IS, the spring effect of the cutter would be eliminated at its lower end and would be afiectecl over its whole length. By eliminating the cutter plate in the present construction and instead cutting slots or notches, l6, ll directly in the lower end of cutter 18, the same loose-coupled fastening is here effected as was shown in my prior application while yet preserving the springpressed expansion quality of the cutter 48. It will also be noted that the present method of fastening the cutter l8 to the shaft [4, as above described, provides a construction which leaves an unobstructed through hole or bore in the cutter, when the cutter and shear member are removed from the head portion 28 for sterilizing or otherwise cleaning, allowing a cylindrical brush or other instrument to be passed completely through the assembled cutter and shear member and permitting a stream of water or other liquid to flow through these bores.

In operation, the motor ll turns the rotor shaft l2 and its extension shaft it, which is rotatably loose-coupled by means of the pin l5 and slots l3, IT, to rotate the cutter i8 journaled in the bore of the shear member [3. As the cutter 18 rotates, the bars 29 of the cutter will have a relatively axial movement in the shear member bore past and over the slots 2'! and bars 28 of the shear member. For a period of time during each revolution of the cutter 18, the bars 29 will be parallel to, and aligned with, the bars 28 of the shear member so that the spaces 39 between the bars 29 will coincide with the slots 2'! of the shear member l9, allowing hair to enter and extend into the bore of the shear member between adjacent bars 29. As the cutter continues its rotational movement, the bars 29 will move over and across the slots 21 and across and through the hair in these slots, clipping said hair with a true shearing action by the engagement and cooperation of the bars 28 and 23.

Besides being strong and sturdy, another improved feature inherent in the present cutter is that it must always have its bars in perfect align ment with its coacting shear member since the pitch of the bars in the improved cutter is determined and conditioned by solid metal. Also in the improved cutter, any wear of the metal will not disturb the pitch of the bars, for reasons stated above and also because the spring pressure of the improved type of cutter is merely that of a leaf spring with an infinite number of bearings or contact points, having its lines of force all in the same curved plane. Furthermore, the improved cutter can be given a spring-pressed expanding movement great enough so that this cutter and its shear member can wear considerably and still operate normally.

Applicant has found by experiment that this improved cutter, when made of thin sheet metal which can be given a spring temper, is susceptible of having a spring pressure and outward movement great enough for the cutter to be worn down until it collapses, having perfect shearing contact until that moment. As such an. amount of wear represents many years of normal service, it will be found that the cooperating shear member will wear out and collapse long before the cutter does as the shear member must necessarily be limited in thickness at its front wall in order to effect a close cutting of the while the cutter can be made relatively thicker.

The cooperating shear member could also be constructed of a thin sheet of steel having bars swaged or otherwise cut in a screw-thread form and then formed into a slitted tube. In such a form, as shown in Fig. 9, the slit or open seam 40 of the tube is then seam-welded, silver-soldered or otherwise permanently fastened and closed so as to present a smooth bore for accommodating the cutter. This tubular shear member 4| is then fastened to a dove-tailed block 42 and the shear member is then internally ground and lapped while offset eccentric to the formed bore so as to thin down the wall adjacent the teeth 43. This method of constructing the shear member provides a definite saving in the cost of material over the method previously shown of making the shear member integral with the dove-tail block. The block 42 may be die-cast or made of molded plastic, with lugs 44 of molten metal or plastic forced into a number of tapered holes 45 in the rear wall of the shear member so that only a thin piece of stainless steel need be used for the shear member and there would be little waste or scrap as there is when the shear member and block are bored and shaped from solid metal.

The construction shown here is susceptible of other modifications. As an instance, the bars of the shear member could alternately be cut at exact right angles to the bore, or at any other small straight angle to this bore, instead of helically or in screw-thread form. But. since the cutter bars will still be in screw-thread form, the slots and spaces 21 and 39 will never perfectly coincide if they are of the same width, so that the spaces 39 between the shear member bars will never be fully open for their whole lengths at any time. This defect can be overcome by making the cutter slots 21 wider than the spaces 39, when a full opening of the spaces 39 will be efiected at each revolution of the cutter. In a certain construction, with the shear member bars at right angles to the axis of the bore and with cutter bars in screw-thread form at a helix angle of about 2 degrees, if the shear member slots are made .008" wide and the cutter slots are made .012 wide, there will be a full opening of the shear member spaces at each revolution of the cutter in the same manner as when helical bars are used for both members.

Various other constructional modifications can be made in the above described device without deviating from the scope of the invention and the appended claims.

I claim:

1. A hair cutter comprising a housing having a rigid back and a tubular extension with an outer bearing wall with spaced helical cutting bars ground thinnest at the surface remote from the back and an inner split tube sprung into the interior of the housing and having helical cutting bars cooperating with the helical cutting bars of the housing, said housing and said split tube being open at one end to permit discharge of cuttings and means connected to the other end of the split tube to rotate the same, the cutting bars of the housing and the cutting bars of the inner tube having cutting edges of substantially the same pitch.

2. In a shaving device a pair of relatively movable coaxial spiral cutting edges, the respective spirals being substantially identical in diameter and in pitch.

3. In a shaving device, a cutting member having a spiral cutting edge and said device being also provided with a cooperating cutting edge that is a segment of a substantially similar coaxial spiral.

4. A dry shaving device having a plurality of spaced stationary cutting edges which are segments of substantially similar coaxial spirals and a complementary spiral cutting edge coaxial with said stationary cutting edges and having the same pitch as the spirals thereof, and means for moving said complementary edge always in the same direction in relation to said stationary cutting edges.

5. In a shaving device, an outer casing having a series of spaced cutting edges and a cutter member rotatable in the casing and having a helical cutting edge coacting with the cutting edges of the casing, the cutting edges of the casing having the same pitch and spacing as the cutting edge of the rotating member.

6. In a shaving device a pair of relatively rotatable coaxial helical members having cutting edges, one being rotatable and fitting snugly within the other, the respective helices being substantially of the same pitch.

7. A power driven razor comprising a casing, a shear member on the casing having a tubular portion with a single series of cutter bars ir screw thread formation and a detachable tubular cutter member having a body of spring metal in said tubular portion and having a portion of said body formed with cutter bars in screw thread formation for cooperation with said first named cutter bars, the remaining portion of said body being slitted from end to end, the walls of the slit being spaced from each other to permit relative movement of said walls, the bars of the shear member and the bars of the tubular cutter member being of substantially identical helical form.

' ROBERT L. PENNEY. 

